1. Field of the Invention
The invention relates to a system for performing physical vapor deposition. More particularly, the invention relates to a method and apparatus for performing high pressure physical vapor deposition.
2. Description of the Background Art
Semiconductor wafer processing systems that perform physical vapor deposition are used for filling trenches and vias with material. When the material is a metal, the filled trenches and vias form interconnect structures between integrated circuit components.
One problem in physical vapor deposition (PVD) systems is that the sputtered particles (atoms) do not always adequately fill a trench or via that is formed in a substrate. Within the feature (trench or via), the sputtered particles deposit along the bottom but unevenly deposit along the sidewalls. As such, the sputtered particles accumulate near the substrate surface before completely filling the feature. If these features are inadequately filled such that voids are formed, then the interconnect structures are defective and generally useless.
Therefore, there is a need to provide a PVD method and apparatus that improves the sidewall coverage of sputtered particles.
This invention provides a method and apparatus for forming void-free interconnects between conducting layers, including apertures such as contacts or vias in high aspect ratio sub-quarter micron applications. The method and apparatus improves the sidewall coverage in physical vapor deposition (PVD) systems. Specifically, the invention comprises a chamber enclosing a target and a substrate. The substrate is supported on a pedestal within the chamber and a sputtering gas is introduced into the chamber. The gas is infused with energy to produce a plasma that sputters the target material onto the substrate.
To facilitate uniform sidewall deposition, the gas pressure in the chamber is substantially higher than the pressure normally used in PVD, and is at least about one torr. To further enhance uniform sidewall deposition, the distance between the target and the substrate is no more than about 50 mm, significantly less than the distance normally found in PVD deposition, such that a substantially larger number of collisions between the sputtered particles and atoms of the plasma occur within the features on the substrate.
A method for sputtering particles from a target onto the substrate having a high aspect ratio feature is also provided. The method comprises the steps of maintaining a relatively high gas pressure within a chamber and sputtering material from the target such that particles sputtered from the target collide with atoms of a plasma within the feature to enhance sidewall deposition.